In preterm human infants, risk of retinopathy of prematurity (ROP) has been linked to small for gestational age, low circulating levels of insulin-like growth factor-1 (IGF-1) and slow postnatal weight gain. To prevent severe ROP, postnatal nutrition in preterm infants is very important.<br /> The aim of this study is to investigate prenatal and postnatal nutrient effects on body weight gain, retinal vascularization and IGF-1 in plasma and retina in oxygen-induced retinopathy rat model.

Methods

Sprague-Dawley rat dams were fed either an unrestricted, isocaloric normal protein (20%) or low protein (10%) diet to cause pup growth restriction from 7 days before gestation. Neonatal rat pups were divided in two groups after birth, smaller litters (7 rats) and larger litters (14 rats) to cause postnatal growth retardation. The dams fed with normal protein diet were used as surrogates. Pups were placed in an Oxycycler chamber that cycled oxygen between 50% and 10% every 24 hours for 14 days. Pups and dams were moved to room air at postnatal (P) 14. At P18, after measuring body weight, the rat pups were sacrificed and blood samples were collected. Retinas in left eyes were collected for ELISA, and retinas in right eyes were fixed, flatmounted and stained with ADPase. Retinal neovascularization (NV) was scored with counting clock hours method. Avascular areas (AVA) were measured as a % of total retinal area (%AVA). Concentration of IGF-1 in plasma and retinas was measured with ELISA. These results were compared in 20%-7rats, 20%-14rats, 10%-7rats and 10%-14rats groups. Statistical analyses were performed with Mann-Whitney’s U test and Kruskal-Wallis test. P value <0.05 was considered significantly.

Results

The pups from dams fed the low protein diet weighted significantly lighter at birth (4.9±0.1g vs. 5.9±0.1g P<0.001). The results on day 18 were shown in table.

Conclusions

Rat pups in 10%-14rats group had low concentration of IGF-1 in retina and plasma. However, these %AVA had no significant difference and the retinal NV was suppressed compared with other groups. These results suggest retinal vascular development in this study could have influenced other than IGF-1 and body weight gain.